1. Field of the Invention
This invention relates to engaging devices of circuit boards, and more particularly, to an engaging device of a circuit board for a server.
2. Description of Related Art
With the development of information technologies, electronic devices are becoming one of the most popular information apparatus in daily life. An electronic device comprises a variety of components, such as a hard disk drive, a power supply and a circuit board, all of which are installed in a housing of the electronic device. The electronic device further comprises a memory, a central processing unit (CPU) and a fan, all of which are installed on the circuit board. As users demand an electronic device to have more functionalities, the electronic device has to comprise more components. However, when the electronic device is operating, static electricity is gathering more and more on the circuit board. Such the static electricity, if gathering on the circuit board continuously, likely causes damages. According to the prior art, the circuit board adopts a standoff to stand itself up and fix itself to the housing of the electronic device. However, the standoff is used to fix the circuit board only, without performing any ground effect. Therefore, a ground structure of the prior art is disclosed for conducting the static electricity gathered on the circuit board to ground, so as to protect the circuit board from the damage of the static electricity.
FIG. 1 is a cross sectional view of a ground structure of a circuit board 5 according to the prior art. As shown in FIG. 1, the ground structure of the circuit board 5 comprises a conductive pole 11 engaged with a housing of an electronic device, and an elastic clamp 12 installed on the circuit board 5. The conductive pole 11 comprises a head portion 112 and a circular concave 111 connected to the head portion 112. The elastic clamp 12 comprises a clamping buckle 122 engaged with a side of a lock hole 53 of the circuit board 5 and contacting with two conductive films 51 installed on the circuit board 5. A convex slice 1211 of the elastic clamp 12 engages itself automatically with a positioning hole 54 of the circuit board 5 to fix the elastic clamp 12. A screw hole 52 of the circuit board 5 passes through the head portion 112 of the conductive pole 11 and disposes itself on the circular concave 111. The circuit board 5 moves toward a direction indicated by arrow A, to enable the head portion 112 of the conductive pole 11 to contact with a top board 123 of the elastic clamp 12 and prop against the lock hole 53 of the circuit board 5, so as to complete positioning and ground processes.
However, in the positioning process, because the top board 123 of the elastic clamp 12 is pushed by the head portion 112 of the conductive pole 11, the elastic clamp 12 will be deformed, enabling a convex slice 1211 of a flat board 121 of the elastic clamp 12 to be departed from the positioning hole 54 of the circuit board 5. Therefore, the elastic clamp 12 does not contact with the conductive film 51 very well, and the conduction of the static electricity is affected.
In view of the above drawbacks, another ground structure of the circuit board 5 comes to the market. Please refer to FIG. 2, which is an explosive view of the ground structure according to the prior art. Compared with the ground structure shown in FIG. 1, the ground structure shown in FIG. 2 further comprises an elastic washer 7 accommodated on the circular concave 211 of the conductive pole 21. The ground structure has a feature that by pushing the flat board 221 of the elastic clamp 22 with the elastic force of the elastic washer 7, the elastic clamp 22 can contact with the conductive film 51 completely, so as to overcome the drawbacks that the elastic clamp 12 does not contact with the conductive film 51 very well.
However, the above ground structure of the circuit board 5 adopts the elastic washer 7 to enable the elastic clamp 22 to contact with the conductive film 51 completely, but the installation of the elastic washer 7 increases the manufacturing cost. Moreover, the elastic washer 7 is easily eroded, so as to impact positioning and ground capabilities of the ground structure. The eroded elastic washer 7 will adhere to the elastic clamp 22, enabling the circuit board 5 hard to be took out. If the circuit board 5 is took out by force, the elastic washer 7 is easily broken. When the elastic clamp 22 is installed on the circuit board 5, the circuit board 5 has to comprise a plurality of positioning holes 54 to allow the elastic clamp 22 to be positioned on the circuit board 5 accurately, this also increasing the manufacturing cost.
Therefore, how to overcome the drawbacks of the prior art is becoming one of the most urgent errands in the art.